VIEWPOINT Commentaries on Viewpoint: Do we need to change the guideline values for determining low bone mineral density in athletes? Commentary on Viewpoint: Do we need to change the guideline values for determining low bone mineral density in athletes? Vera Weijer, 1,2 Luuk Hilkens, 1,2 Naomi Brinkmans, 1 and Jan-Willem van Dijk 1 1 School of Sport and Exercise, HAN University of Applied Sciences, Nijmegen, The Netherlands; and 2 Department of Human Biology, NUTRIM, Maastricht University Medical Centre þ , Maastricht, The Netherlands TO THE EDITOR: The Viewpoint by Jonvik et al. (1) proposes to change the guidelines to interpret athletes’ bone mineral density (BMD) Z-scores in low- versus high-impact sports. This proposal is mainly based on the potential role of BMD as a marker of low energy availability (LEA)/relative energy deficiency in sport (RED-S). It can be argued, however, that the primary function of BMD measurements is to analyze the risk of (osteoporotic) fractures in an individual (2). In this regard, BMD Z-scores seem to be related to (stress) fracture risk, independent of sports discipline (3). Furthermore, achieving a high peak bone mass, and preventing low abso- lute BMD, in early adulthood may prevent osteoporosis and fractures later in life (4,5). These arguments do not support the use of sport-specific guidelines for the interpretation of BMD Z-scores. Nevertheless, we agree with Jonvik et al. (1) that high-impact sports could mask the presence of LEA/ RED-S when using population-based Z-scores. Some poten- tial pitfalls of this approach should be noted as well. First, the distinction between low- and high-impact sports is not always clear because low-impact sports can also include high-impact training. Second, sport-specific impact can dif- ferentially affect BMD status at various measurement sites. Finally, BMD changes occur slowly, which complicates the early detection and treatment of LEA by this instrument. In conclusion, sport-specific reference values could be a valua- ble adjunct in the diagnosis of LEA, but probably less impor- tant with regard to (stress) fracture risk. For early detection and prevention of LEA, research might need to focus more on the validation and use of objective blood markers. DISCLOSURES No conflicts of interest, financial or otherwise, are declared by the authors. REFERENCES 1. Jonvik KL, Torstveit MK, Sundgot-Borgen JK, Mathisen TF. Do we need to change the guideline values for determining low bone mineral density in athletes? J Appl Physiol (1985). doi:10.1152/ japplphysiol.00851.2021. 2. Lewiecki EM, Gordon CM, Baim S, Leonard MB, Bishop NJ, Bianchi M-L, Kalkwarf HJ, Langman CB, Plotkin H, Rauch F, Zemel BS, Binkley N, Bilezikian JP, Kendler DL, Hans DB, Silverman S. International Society for Clinical Densitometry 2007 adult and pediatric official positions. Bone 43: 1115–1121, 2008. doi:10.1016/j.bone.2008.08.106. 3. Bennell K, Matheson G, Meeuwisse W, Brukner P. Risk factors for stress fractures. Sports Med 28: 91–122, 1999. doi:10.2165/ 00007256-199928020-00004. 4. Weaver CM, Gordon CM, Janz KF, Kalkwarf HJ, Lappe JM, Lewis R, O’Karma M, Wallace TC, Zemel BS. The National Osteoporosis Foundation’s position statement on peak bone mass development and lifestyle factors: a systematic review and implementation recommendations. Osteoporosis Int 27: 1281– 1386, 2016. doi:10.1007/s00198-015-3440-3. 5. Hilkens L, Knuiman P, Heijboer M, Kempers R, Jeukendrup AE, van Loon LJC, van Dijk J-W. Fragile bones of elite cyclists: to treat or not to treat? J Appl Physiol (1985) 131: 26–28, 2021. doi:10.1152/japplphysiol.01034.2020. Z-scores for athletes: The need of transition from blanket to bracket approach Shival Srivastav and Mahesh Arjundan Gadhvi Department of Physiology, All India Institute of Medical Sciences, Jodhpur, India TO THE EDITOR: The effect of physical activity on bone mineral density (BMD) is not uniform across different sports (1). The net “osteogenic” effect of different sports is multifactorial and may be contingent on diverse physi- ological factors including, but not limited to, age and gen- der (2). In addition, genetic factors may also be at play. Protracted stretches of low energy availability (LEA) fol- lowing engagement in sports may compound the problem (3,4), predisposing athletes to risk of osteoporosis and stress fractures. In light of the present information, a blanket approach to identify athletes at risk of reduced bone mineral density (BMD) needs to be repudiated. There is a strong need to define activity-specific Z-scores for athletes. Also, the afore- mentioned miscellaneous determinants should also be cogi- tated upon. This will facilitate early identification of at-risk individu- als and enable institution of corrective measures. As pro- posed by Jonvik et al. (4), this is possible only by global congregation of sports and exercise physiology experts. Their collective efforts should culminate in generation of sport/event-specific cumulative data while also factoring in http://www.jap.org 8750-7587/22 Copyright © 2022 The Authors. Licensed under Creative Commons Attribution CC-BY 4.0. Published by the American Physiological Society. 1323 J Appl Physiol 132: 1323–1324, 2022. doi:10.1152/japplphysiol.00203.2022 Downloaded from journals.physiology.org/journal/jappl (054.224.113.144) on June 16, 2022.